From: Valentin Schneider <valentin.schneider@arm.com>
To: Vincent Donnefort <vincent.donnefort@arm.com>
Cc: linux-kernel@vger.kernel.org, Qian Cai <cai@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
tglx@linutronix.de, mingo@kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, tj@kernel.org, ouwen210@hotmail.com
Subject: Re: [PATCH 2/2] workqueue: Fix affinity of kworkers attached during late hotplug
Date: Fri, 11 Dec 2020 13:13:35 +0000 [thread overview]
Message-ID: <jhjmtyktri8.mognet@arm.com> (raw)
In-Reply-To: <jhjo8j0tsia.mognet@arm.com>
On 11/12/20 12:51, Valentin Schneider wrote:
>> In that case maybe we should check for the cpu_active_mask here too ?
>
> Looking at it again, I think we might need to.
>
> IIUC you can end up with pools bound to a single NUMA node (?). In that
> case, say the last CPU of a node is going down, then:
>
> workqueue_offline_cpu()
> wq_update_unbound_numa()
> alloc_unbound_pwq()
> get_unbound_pool()
>
> would still pick that node, because it doesn't look at the online / active
> mask. And at this point, we would affine the
> kworkers to that node, and we're back to having kworkers enqueued on a
> (!active, online) CPU that is going down...
Assuming a node covers at least 2 CPUs, that can't actually happen per
is_cpu_allowed().
next prev parent reply other threads:[~2020-12-11 13:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-10 16:38 [PATCH 0/2] workqueue: Fix migrate_disable hotplug changes vs kworker affinity Valentin Schneider
2020-12-10 16:38 ` [PATCH 1/2] stop_machine: Add caller debug info to queue_stop_cpus_work Valentin Schneider
2021-03-23 15:08 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-12-10 16:38 ` [PATCH 2/2] workqueue: Fix affinity of kworkers attached during late hotplug Valentin Schneider
2020-12-11 11:39 ` Vincent Donnefort
2020-12-11 12:41 ` Peter Zijlstra
2020-12-11 12:51 ` Peter Zijlstra
2020-12-11 12:51 ` Valentin Schneider
2020-12-11 13:13 ` Valentin Schneider [this message]
2020-12-11 13:16 ` Vincent Donnefort
2020-12-11 12:52 ` [PATCH 0/2] workqueue: Fix migrate_disable hotplug changes vs kworker affinity Peter Zijlstra
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